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Manual 35018V1
505XT Digital Control System for Steam Turbines
Woodward
177
In the configuration of Speed Setpoints be sure that the Overspeed
Test Limit rpm value is above the expected Overspeed setting of the
external safety overspeed protection device.
It is recommended to perform Overspeed Tests from these screens, either at the control (preferred) or via
the RemoteView service tool. Alternatively the turbine’s overspeed logic and circuitry can be tested
remotely, by programming an Overspeed Test contact input. The Overspeed Test contact functions as
the enable external test on the display. When the conditions outlined in the above procedure are met,
closing this contact allows the Speed set point to be increased up to the “Overspeed Test limit” setting.
The testing procedure is similar to using the OSPD key. An Overspeed Test Enabled relay can be
programmed to provide the status feedback that testing is enabled.
The Overspeed Test function cannot be performed over the Modbus communications, however, the
Overspeed Test Permissive, Overspeed Test In Progress, Overspeed Alarm, and Overspeed Trip
indications are available through Modbus.
Stop Key
The STOP key is used to perform a controlled/manual turbine shutdown or stop. To perform a Manual
Shutdown, press the STOP key and confirm from the keypad or close the Controlled Shutdown contact
input (if programmed) or select Controlled Shutdown from a Modbus communications link. Once initiated,
the display dialog box will change to give the user the option to abort the Normal stop sequence. This
dialog box will close after 10 seconds, but can be reopened by pressing the STOP key. This function can
be also be stopped by opening the contact or selecting Abort Controlled Shutdown from a Modbus
communications link.
Alarm Summary
The ALARM screen is always available with the VIEW button under the ALARM LED. When an alarm is
detected, it gets latched in the event logic, the Alarm relay is energized, and the ALARM LED illuminates
(Yellow). The cause of the event will be indicated with an Event ID, description and time/date stamp on
the Alarm Summary page. The list will always place the first event at the top of the list, if more than one
alarm condition is present they will all be listed with their corresponding time stamp.
To clear any alarms that are no longer present, press the RESET key, close the Reset contact input, or
select Reset from either Modbus communications link. If the cause of the event has been corrected the
alarm will clear, it not it will remain and the time-stamp will remain unchanged.
Figure 5-30. ALARM Screen